Speaker system

ABSTRACT

A loudspeaker system capable of simultaneously providing listeners with a listening environment not giving them a feeling of strangeness. The loudspeaker system ( 100 ) comprises drive motors ( 111  to  113, 121  to  123 ) for so driving at least first R-channel loudspeaker ( 101 ) that the current first listening position is substantially included in the perpendicularly bisecting plane of a line joining the intersecting point of the first R-channel speaker ( 101 ) and its directivity axis and the intersecting point of the second R-channel loudspeaker ( 120 ) and its directivity axis and so driving at least fourth L-channel loudspeaker ( 104 ) that the current second listening point is substantially included in the perpendicularly bisecting plane of the line joining the intersecting point of a third L-channel loudspeaker ( 103 ) and its directivity axis and the intersecting point of a fourth L-channel loudspeaker ( 104 ) and its directivity axis. The loudspeaker system ( 100 ) further comprises their motor driver section ( 130 ).

TECHNICAL FIELD

The present invention relates a speaker system that includes a pair ofspeaker units each including at least two speakers.

BACKGROUND ART

A conventional speaker system includes, for example, an L channelspeaker unit, an R channel speaker unit and a center speaker unit (forexample, see Patent Document 1). Each of the above three speaker unitsis arranged in the center of positions ahead of the driver's seat andpassenger seat of a vehicle. The L channel speaker unit is directedtoward a direction in which the directivity axis of the L channelspeaker unit is rotated counterclockwise in the horizontal directionwith respect to the traveling direction of the vehicle and in which thedirectivity axis is inclined at a predetermined angle to the verticaldirection with respect to the traveling direction of the vehicle. The Rchannel speaker unit is directed toward a direction in which thedirectivity axis of the R channel speaker unit is rotated clockwise inthe horizontal direction with respect the traveling direction of thevehicle and in which the directivity axis is inclined at a predeterminedangle in the vertical direction with respect to the traveling directionof the vehicle. The center speaker unit outputs an −L-R signal obtainedby adding an −L signal which is a reverse phase signal of an L channelsignal and an −R signal which is a reverse phase signal of the R channelsignal.

Patent Document 1: Japanese Patent Application Laid-Open No. 2004-289341DISCLOSURE OF INVENTION Problems to be Solved by the Invention

With such a conventional speaker system mounted in a vehicle, given thata difference (path length difference) is caused between the lengths ofthe paths for the L and R channel signals through which the Both signalsreaches the listener in the driver's seat, a phase difference and delayare caused between the both channel signals before they reach thelistener. The same applies to the listener in the front passenger seat.There is a problem that listeners feel a sense of discomfort listeningto audio due to the above phase difference and delay.

In view of the above, it is therefore an object of the present inventionto provide a speaker system that makes it possible to provide alistening environment which does not give a sense of discomfort to aplurality of listeners.

Means for Solving the Problem

In order to achieve the above object, the speaker system according tothe present invention comprises: a first speaker unit including a firstspeaker outputting a sound to be heard in a first listening position anda second speaker outputting a sound to be heard in a second listeningposition; a second speaker unit including a third speaker outputting asound to be heard in the first listening position and a fourth speakeroutputting a sound to be heard in the second listening position; and adriving section configured to drive at least the first speaker such thatthe current first listening position is substantially included in avertical bisector plane of a line connecting an intersection of thefirst speaker and a directivity axis of the first speaker and anintersection of the second speaker and a directivity axis of the secondspeaker, and to drive at least the fourth speaker such that the currentsecond listening position is substantially included in a perpendicularbisector plane of a line connecting an intersection of the third speakerand a directivity axis of the third speaker and an intersection of thefourth speaker and a directivity axis of the fourth speaker.

ADVANTAGEOUS EFFECT OF THE INVENTION

In the above speaker system, at least the first speaker and the fourthspeaker are driven as described above. Consequently, sounds without aphase difference and delay are more easily provided to the listeners atthe first listening position and the second listening position. In thisway, according to the present invention, it is possible to provide aspeaker system that is able to provide to a plurality of listeners atthe same time a listening environment which does not give a sense ofdiscomfort.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating from above the interior of a vehiclemounting a speaker system according to Embodiment 1 of the presentinvention;

FIG. 2 is a diagram illustrating the overall configuration of thespeaker system according to above Embodiment 1;

FIG. 3 is a plan view illustrating positions of the listener and thespeaker unit of the speaker system according to above Embodiment 1;

FIG. 4 is a schematic view illustrating the relationship between theposition of the listener and the direction of the speaker unit of thespeaker system according to above Embodiment 1;

FIG. 5 is a schematic view illustrating the relationship between thepositions of the speaker unit and the listener in case that the positionof the listener of the speaker system according to above Embodiment 1changes back and forth;

FIG. 6 is a schematic view illustrating the relationship between thepositions of the speaker unit and the listener in case that the positionof the listener of the speaker system according to above Embodiment 1changes right and left;

FIG. 7 illustrates the directivity axis of the speaker in case that theposition of the listener of the speaker system according to aboveEmbodiment 1 changes up and down;

FIG. 8 is a perspective view of the relationship between the positionsof the speaker unit and the listener in case that the position of thelistener of the speaker system according to above Embodiment 1 changesright and left;

FIG. 9 is a schematic view illustrating operations of speakers andspeaker units of the speaker system according to above Embodiment 1;

FIG. 10 is a diagram illustrating a table of control content of“rotation,” “opening angle” and “angle of elevation” corresponding to achange in the position of the listener of the speaker system accordingto above Embodiment 1;

FIG. 11 is a diagram illustrating a null plane formed on a plane atequal distances from two sound sources of the speaker system accordingto above Embodiment 1;

FIG. 12 is a diagram illustrating a null plane formed on a plane atequal distances from two sound sources of the speaker system accordingto above Embodiment 1;

FIG. 13 is a diagram illustrating a null plane of speakers in a statewhere there is no difference as to angle of elevation in the speakersystem according to above Embodiment 1;

FIG. 14 is a diagram illustrating a null plane of speakers in a statewhere there is a difference of angle of elevation in the speaker systemaccording to above Embodiment 1;

FIG. 15 is a diagram illustrating correction of the path length due tothe phase difference in the speaker system according to above Embodiment1;

FIG. 16 is a schematic view illustrating an adjusting method of applyingthe speaker system according to above Embodiment 1;

FIG. 17 is a diagram illustrating a table of control content of thedifferences between angles of elevations in the position of the listener(the position of the head) of the speaker system according to aboveEmbodiment 1;

FIG. 18 is a flowchart illustrating automatic adjustment processing ofthe speaker system according to above Embodiment 1;

FIG. 19 is a diagram illustrating from above the interior of a vehiclemounting the speaker system according to Embodiment 2 of the presentinvention;

FIG. 20 is a diagram illustrating the overall configuration of thespeaker system according to above Embodiment 2; and

FIG. 21 is a flowchart illustrating automatic adjustment processing ofthe speaker system according to above Embodiment 2.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described in detail belowwith reference to the drawings.

Embodiment 1

FIG. 1 is a schematic view illustrating a speaker system 100 accordingto Embodiment 1 of the present invention and the interior of a vehiclemounting the speaker system 100 from above. FIG. 2 is a block diagramillustrating the speaker system 100 shown in FIG. 1 and peripheralcomponents of the speaker system 100.

In FIG. 1 and FIG. 2, the speaker system 100 comprises a first R channelspeaker 101, a second R channel speaker 102, a third L channel speaker103 and a fourth L channel speaker 104, each of the speakers 101 to 104outputting sound of the middle and high frequency range (about 200 Hz to20 kHz).

The first R channel speaker 101 is arranged virtually in front of thedriver's seat of the vehicle (for example, in/on a dashboard 200) in aninitial state and outputs sound based on the in-phase signal of the Rchannel signal (hereinafter referred to as “in-phase signal (R)”) fromthe sound source.

Further, the second R channel speaker 102 is arranged in an initialstate in a position in plane symmetry with the first R channel speaker101 with respect to the first virtual plane and is arranged virtually infront of the driver's seat, and outputs sound based on the reverse phasesignal (hereinafter “reverse phase signal (R)”) having a reverse phasewith respect to the above in-phase signal (R).

Furthermore, the above first virtual plane will be referred to as the“first reference plane c” in the following description. With the presentembodiment, this first reference plane c is parallel or virtuallyparallel to the longitudinal intermedian plane e of the vehicle,includes the listening position (hereinafter referred to as “the firstlistening position”) for the listener sitting in the driver's seat andpasses the middle point of the first and second R channel speakers 101and 102. Further, as illustrated with the present embodiment, the firstlistening position is determined in advance around the head of thelistener sitting in the driver's seat.

Furthermore, the third L channel speaker 103 is arranged virtually infront of the front passenger seat next to the driver's seat (forexample, in/on the dashboard 200) in an initial state, and outputs soundbased on the in-phase signal of the L channel signal (hereinafterreferred to as “in-phase signal (L)”) from the same sound source asabove.

The fourth L channel speaker 104 is arranged in an initial state in aposition in plane symmetry with the third L channel speaker 103 withrespect to the second virtual plane and is arranged virtually in frontof the front passenger seat, and outputs sound based on the reversephase signal (hereinafter referred to as “reverse phase signal (L)”)having a reverse phase with respect to the above in-phase signal (L).

The above second virtual plane will be referred to as “second referenceplane d” in the following description. With the present embodiment, thissecond reference plane d is parallel or virtually parallel to thelongitudinal intermedian plane e of the vehicle, includes the listeningposition for the listener sitting in the front passenger seat(hereinafter referred to as “the second listening position”) and passesthe middle point of the third and fourth L channel speakers 103 and 104.Further, as illustrated with the present embodiment, the secondlistening position is determined in advance around the head of thelistener sitting in the front passenger seat.

As described above, the first R channel speaker 101 outputs sound basedon the in-phase signal (R) and the second R channel speaker 102 outputssound based on the reverse phase signal (R). Consequently, on and nearthe first reference plane c, sound based on the in-phase signal (R) andsound based on the reverse signal (R) cancel each other and the listenersitting in the driver's seat feels like sound does not come from thefront. A plane in which sound based on the in-phase signal and soundbased on the reverse phase signal of the in-phase signal cancel eachother, will be referred to as a “null plane.” This null plane will bedescribed later referring to FIG. 11 to FIG. 14. In FIG. 1, the firstreference plane c is a null plane in which sound based on the in-phasesignal (R) and sound based on the reverse phase signal (R) cancel eachother. In the null plane, the listener feels like speakers installedvirtually in front of the listener do not exist in hearing and the soundcomes from the right and left speakers (one is a virtual image). Giventhat the same phenomenon occurs in the third L channel speaker 103 andfourth L channel speaker 104, the listener sitting in the frontpassenger seat feels like sound does not come from the front of thelistener. In FIG. 1, the second reference plane d is a null plane inwhich sound based on the in-phase signal (L) and sound based on thereverse phase signal (L) cancel each other.

A pair of the first R channel speaker 101 and the second R channelspeaker 102 composes a speaker unit SP1 of the driver's seat side, and apair of the third L channel speaker 103 and the fourth L channel speaker104 composes a speaker unit SP2 of the front passenger seat side. Inthis way, the speaker units SP1 and SP2 are arranged in the driver'sseat side and in the front passenger seat side of the dashboard 200,respectively. Further, the first R channel speaker 101 and the third Lchannel speaker 103 compose speakers for the listener (driver) in thedriver's seat, and the second R channel speaker 102 and the fourth Lchannel speaker 104 compose speakers for the listener in the frontpassenger seat.

Further, in the first R channel speaker 101, driving motor 111 forchanging the angle (hereinafter referred to as the “opening angle”) withrespect to the first reference plane c and a driving motor 112 forchanging at least the difference of the angle (hereinafter referred toas the “difference of angle of elevation”) of the directivity axis ofthe first R channel speaker 101 in the perpendicular direction withrespect to the directivity axis of the second R channel speaker 102, areinstalled. In the speaker unit SP1, a driving motor 113 that, whilemaintaining the difference of angle of elevation between the directivityaxis of the first R channel speaker 101 and the directivity axis of thesecond R channel speaker 102, changes both the direction of thedirectivity axis of the first R channel speaker 101 and the direction ofthe directivity axis of the second R channel speaker 102 with respect tothe plane where the speaker unit SP1 is installed. In this way, in thespeaker unit SP1, the driving motor 111 for changing the opening angleand the driving motor 112 for changing the above difference of angle ofelevation are installed only in the first R channel speaker 101, and, inthe second R channel speaker 102, driving motors for changing theseopening angle and difference of angle of elevation are not installed.Further, the angle of elevation of the overall speaker unit SP1 can bechanged by the driving motor 113.

Similarly, in the fourth L channel speaker 104, a driving motor 121 forchanging the angle (i.e. opening angle) with respect to the secondreference plane d and a driving motor 122 for changing at least thedifference of the angle (i.e. difference of angle of elevation) of thedirectivity axis of the fourth L channel speaker 104 in theperpendicular direction with respect to the directivity axis of thethird L channel speaker 103, are installed. In the speaker unit SP2, adriving motor 123 is installed in order to changes, while maintainingthe difference of angle of elevation between the directivity axis of thefourth L channel speaker 104 and the directivity axis of the third Lchannel speaker 103, the directions of the directivity axis of thefourth L channel speaker 104 and the directivity axis of the third Lchannel speaker 103 with respect to the plane where the speaker unit SP2is arranged. In this way, in the speaker unit SP2, the driving motor 121for changing the opening angle and the driving motor 122 for changingthe difference of angle of elevation are installed only in the fourth Lchannel speaker 104, and, in the third L channel speaker 103, drivingmotors for changing these opening angle and difference of angle ofelevation are not installed. Further, the angle of elevation of theoverall speaker unit SP2 can be changed by the driving motor 123. Theabove driving motors 111 to 113 and 121 to 123 are composed of, forexample, stepping motors and enable precise control.

The opening angle, the difference of angle of elevation and the angle ofelevation as mentioned above will be described later referring to FIG. 9to FIG. 14 and FIG. 16.

Further, in FIG. 1 and FIG. 2, the speaker system 100 comprises a motordriver section 130 that drives the driving motors 111 and 121 forchanging the opening angles, the driving motors 112 and 122 for changingthe differences of angles of elevations and the driving motors 113 and123 for changing the angles of elevations of speaker units SP1 and SP2;and a sound processing section 141 that carries out signal processing ofa 2-channel (i.e. L channel and R channel) signal from a sound inputsection 140, to which the sound source composed of the 2-channel signalis inputted, and generates the in-phase signal (R), the reverse phasesignal (R), the in-phase signal (L) and the reverse phase signal (L) asmentioned above.

The in-phase signal (R), the reverse phase signal (R), the in-phasesignal (L) and the reverse phase signal (L) that are generated by soundprocessing section 141, are outputted to the first R channel speaker101, the second R channel speaker 102, the third L channel speaker 103and the fourth L channel speaker 104, respectively.

The sound input section 140 is an input terminal that receives as inputa sound source from audio devices such as CD players, DVD players, MDplayers, cassette decks, radios, television receivers and semiconductormemory audio devices or speech input apparatuses such as microphones.Further, the sound input section 140 may be an audio device or speechinput apparatus itself.

Further, a sound processing section 141 includes delay units (not shown)and can produce phase differences (i.e. delay) between the outputs ofthe first R channel speaker 101 and the second R channel speaker 102 orbetween the outputs of the third L channel speaker 103 and the fourth Lchannel speaker 104 by the delay units. It is possible to adjust a shiftin sounds due to the difference between the right and left paths byadjusting the phase difference (i.e. delay).

In FIG. 2, in the speaker system 100 in the vehicle, a controllingsection 150 that controls, for example, the opening angle depending onthe listening positions of a plurality of listeners and a positiondetecting section 160 that receives signals from contact switches 161and 162 which detect the front-back position of a seat and the recliningangle of the seat and detects the location of the head of the seatedlistener.

The controlling section 150 includes a microprocessor, acquires headposition information of the listener from the position detecting section160 by executing a control program to be described later referring toFIG. 18, refers to various setting information and a table stored in astoring medium (for example, semiconductor memory) (not shown), outputsto, the motor driving section 130 the control commands for adjusting theopening angles of the speakers 101 to 104, the differences of angles ofelevations between the speakers 101 to 104 and the angles of elevationsof the speaker units SP1 and SP2 and outputs to the sound processingsection 141 the control signal for adjusting sound volumes from thespeakers 101 to 104 and the phases of output sounds from the speakers101 to 104, depending on the current listening position. The motordriver section 130 precisely controls the drive amount of thecorresponding driving motor according to the above control commands andchanges the opening angles of the speakers 101 to 104, the differencesof angles of elevations between the speakers 101 to 104 and the anglesof elevations of the speaker units SP1 and SP2 to target values.Further, the sound processing section 141 changes the sound volumes tobe outputted from the speakers 101 to 104 and the phases of sounds to beoutputted from these speakers 101 to 104, according to the controlsignals from the controlling section 150. Further, the sound volume andthe phase are controlled by the sound processing section 141, in thiscase, to adjust the sound pressure level and a shift in phases caused byadjustment of the above opening angle, the differences of angles ofelevations and the angles of elevations.

Further, the controlling section 150 is a controlling apparatus thatcontrols the speaker system 100 and may be installed outside the speakersystem 100 or may be incorporated inside. Further, the controllingsection 150 may be incorporated in an audio device such as a car audiodevice. In this case, the controlling section of the audio device suchas the car audio device executes a control program to be described laterin FIG. 18.

Further, with the present embodiment, the position detecting section 160detects the current listening position (for example, the position of thehead of the listener) based on detected signals from the contactswitches 161 and 162 installed in the seat. The method of detecting theposition of the head of the listener from the seat position provides aneffect of realizing the present invention at a lower cost and at moreease. Further, although only the contact switches 161 and 162 in oneseat are shown in FIG. 2, in practice, a set of contact switches 161 and162 are installed in the driver's seat and in the front passenger seat.That is, the current first listening position is detected based ondetected signals outputted from the contact switches 161 and 162 of thedriver's seat side and the current second listening position is detectedbased on detected signals from a set of contact switches of the frontpassenger seat side.

Further, a configuration may be possible where, for example, a camerathat takes an image of the vicinity of the listener's head and an imageprocessing section that recognizes an image of positions of the head andears from this image are installed instead of the position detectingsection 160 to directly detect the positions of the head and ears of thelistener.

[Basic Installment of Speakers and Speaker Units]

The first R channel speaker 101 and the second R channel speaker 102 aremounted in the dashboard 200 of the driver's seat side such that theopening angle and the angle of elevation described below are formed.Similarly, the third L channel speaker 103 and the fourth L channelspeaker 104 are mounted in the dashboard 200 of the front passenger seatside such that the opening angle and the angle of elevation describedbelow are formed.

(1) The first speaker unit SP1 is arranged in a location where anextension line of a bisector 170 of the opening angle, which is formedby the directivity axis of the first R channel speaker 101 and thedirectivity axis of the second R channel speaker 102, is parallel orvirtually parallel to the longitudinal intermedian plane e of thevehicle and passes the first listening position. Further, the extensionline of the bisector 170 is included in the first reference plane c inwhich the in-phase signal (R) and its reverse phase signal (R) canceleach other. Similarly, the second speaker unit SP2 is arranged in alocation where an extension line of a bisector 180 of the opening angle,which is formed by the directivity axis of the third L channel speaker103 and the directivity axis of the fourth L channel speaker 104, isparallel or virtually parallel to the longitudinal intermedian plane eof the vehicle and passes the second listening position. The extensionline of the bisector 180 is included in the second reference plane d inwhich the in-phase signal (L) and its reverse phase signal (L) canceleach other. By this means, the first R channel speaker 101 and thesecond R channel speaker 102 are arranged virtually in front of thedriver, and the third L channel speaker 103 and the fourth L channelspeaker 104 are arranged virtually in front of the listener in the frontpassenger seat. Consequently, as described above, each listener sittingin the driver's seat and the front passenger seat feels like sound doesnot come from the front.

(2) The position of the first speaker unit SP1 is determined such thatthe distance of a path 171 through which sound is reflected by a rightside glass 210 and reaches from the first R channel speaker 101 theright ear of the driver and the distance of a path 172 through whichsound reaches from the third L channel speaker 103 directly the left earof the driver, are equal. Similarly, the position of the second speakerunit SP2 is determined such that the distance of a path 173 throughwhich sound reaches from the second R channel speaker 102 directly theright ear of the listener in the front passenger seat and the distanceof a path 174 through which sound is reflected by a left side glass 220and reaches from the fourth L channel speaker 104 the left ear of thedriver, are equal.

(3) The first speaker unit SP1 and the second speaker unit SP2 arearranged in positions in plane symmetry with each other with respect tothe longitudinal intermedian plane e including the longitudinalintermedian line of the vehicle.

Depending on the size of the vehicular interior, the position of theseat and the shape of the dashboard, there are cases where all of theabove arrangement conditions (1) to (3) are not necessarily satisfied.In these cases, the first R channel speaker 101, the second R channelspeaker 102, the third L channel speaker 103 and the fourth L channelspeaker 104 are mounted by adjusting the arrangement and directions suchthat the above arrangement conditions (1) to (3) are satisfied as muchas possible. What matters in hearing is the condition of above (2) thatthe distance of the path through which sound is reflected by the sideglasses 210 and 220 and reaches the listener and the distance of thepath through which sound reaches the listener directly, are equal. Toprioritize this condition, a method of arranging the first R channelspeaker 101 and the second R channel speaker 102, and the third Lchannel speaker 103 and the fourth L channel speaker 104 on thedashboard 200 by slightly shifting these speakers right and left or backand forth from the front of the driver or the listener in the frontpassenger seat, may be adopted. In this case, the first R channelspeaker 101, the second R channel speaker 102, the third L channelspeaker 103 and the fourth L channel speaker 104 may not be directedtoward the listener in the driver's seat (i.e. driver) and the listenerin the front passenger seat.

If the first R channel speaker 101, the second R channel speaker 102,the third L channel speaker 103 and the fourth L channel speaker 104 aresuitably arranged on the dashboard 200 such that the above arrangementconditions (1) and (2) are satisfied, the driver does not listen tosound from the first R channel speaker 101 directly but listens to thesound reflected by the side glass 210. Consequently, the listener feelslike sound based on the in-phase signal (R) comes from a virtual image105 of the first R channel speaker 101 in the front right outside thevehicle. The listener sitting in the driver's seat feels like thevirtual image 105 of this first R channel speaker 101 is in a positionin symmetry with the third L channel speaker 103 with respect to thefirst reference plane c. By listening to sound from the virtual image105 of this first R channel speaker 101 and sound from the third Lchannel speaker 103, the listener sitting in the driver's seat is ableto listen to wide stereo sound in the narrow space in the vehicle inwhich installation of speakers is significantly restricted.

The second speaker unit SP2 is arranged in a position in symmetry withthe first speaker unit SP1 with respect to the longitudinal intermedianplane e of the vehicle, the listener in the front passenger seatrecognizes that there is a virtual image 106 of the fourth L channelspeaker 104 in the front left outside the vehicle. Consequently, thelistener sitting in the front passenger seat is able to listen to widestereo sound, like the listener sitting in the driver's seat.

In this way, the speaker system 100 comprises the speaker unit SP1composed of the first R channel speaker 101 that radiates the in-phase Rchannel signal and the second R channel speaker 102 that radiates thereverse phase R channel signal, and the speaker unit SP2 composed of thethird L channel speaker 103 that radiates the in-phase L channel signaland the fourth L channel speaker 104 that radiates the reverse phase Lchannel signal. In the speaker unit SP1, the first R channel speaker 101and the second R channel speaker 102 are in plane symmetry with respectto the first reference plane c including the current first listeningposition for the driver, and are arranged such that sound outputted fromthe first R channel speaker 101 is reflected by the side glass 210 andreaches the first listening position. The speaker unit SP2 is arrangedin a position in plane symmetry with the first speaker unit SP1 withrespect to the longitudinal intermedian plane e of the vehicle, thethird L channel speaker 103 and the fourth L channel speaker 104 are inplane symmetry with respect to the second reference planed including thecurrent second listening position for the listener in the frontpassenger seat and are arranged such that sound outputted from thefourth L channel speaker 104 is reflected by the side glass 220 andreaches the second listening position.

Further, the first R channel speaker 101 and the third L channel speaker103 are arranged such that the distance through which sound outputtedfrom the first R channel speaker 101 is reflected by the side glass 210and reaches the first listening position and the distance through whichsound outputted from the third L channel speaker 103 reaches directlythe first listening position, are equal. The second R channel speaker102 and the fourth L channel speaker 104 are arranged according to thesame relationship as between the positions of the first R channelspeaker 101 and the third L channel speaker 103.

By the above, it is possible to provide to the listeners, the sound ofthe R channel and the sound of the L channel with practically no phasedifference and no delay.

The listeners do not feel a sense of discomfort listening to audio.Further, the listener sitting in the front passenger seat is also ableto listen to wide stereo sound like the listener sitting in the driver'sseat.

[Detailed Arrangement of Speakers and Speaker Units]

FIG. 3 is a plan view illustrating the positions of the speaker unit andthe listener, employing an example of the relationship between thepositions of the speaker unit SP1 of the driver's seat side and thelistener P1 in the driver's seat (i.e. driver).

As shown in FIG. 3, the speaker unit SP1 and the listener P1 in thedriver's seat virtually face each other. Further, the reference symbol“a” is assigned to the directivity axis of the first R channel speaker101 that radiates sound based on the in-phase signal (R) and thereference symbol “b” is assigned to the directivity axis of the second Rchannel speaker 102 that radiates sound based on the reverse phasesignal (R). The reference symbol “c” is assigned to the above-describedfirst reference plane. The first reference plane c is a null plane inwhich sound based on the in-phase signal (R) and sound based on thereverse phase signal (R) cancel each other. Further, assuming that theangle formed by the directivity axis a and the first reference plane cisrv1 and the angle formed by the directivity axis b and the firstreference plane c is rv2, the condition of the following equation 1 forproviding an effect of making the listener P1 sitting in the driver'sseat feel like sound does not come from the front, is established.

rv1=rv2  (Equation 1)

Further, if the above equation 1 is satisfied, the speaker unit SP1 andthe listener P1 need not to face each other as shown in, for example,FIG. 3.

Although the positions of the speaker unit SP1 of the driver's seat sideand the listener P1 in the driver's seat (i.e. driver) have beendescribed above, the same applies to the listener in the front passengerseat and the speaker unit SP2 of the front passenger seat side, that is,the in-phase signal (L) and the reverse phase signal (R).

FIG. 4 is a schematic view illustrating the relationship between thedirection of a speaker unit and the location of the listener, employingan example of the relationship between the positions of the speaker unitSP1 of the driver's seat side, the listener P1 in the driver's seat(i.e. driver) and the listener P2 in the front passenger seat.

In FIG. 4, the speaker unit SP1 of the driver's seat side is installedon the dashboard 200 shown in FIG. 1. Further, the reflecting plane A ofFIG. 4 is the side glass 210 of FIG. 1. This space inside the vehicle isrepresented by X and Y. In the width X in the space in the vehicle, tothe reference point of the reflecting plane A, there are the distance x3from the speaker unit SP1 of the driver's seat side, the distance x1from the listener P1 in the driver's seat and the distance x2 from thelistener P2 in the front passenger seat. Further, in the depth Y in thespace in the vehicle, there is the distance y1 from the listener P1 inthe driver's seat to the reference point of the speaker unit SP1 andthere is the distance y2 from the listener P2 in the front passengerseat to the reference point of speaker unit SP1.

The reference symbol “α” (see the dotted line) is assigned to the paththrough which the sound outputted from the first R channel speaker 101composing the speaker unit SP1 (i.e. the in-phase signal (R)) isreflected by the reflecting plane A and reaches the listener P1 in thedriver's seat, and the reference symbol “β” (see the dotted line) isassigned to the path through which the sound outputted from the second Rchannel speaker 102 (i.e. the reverse phase signal (R)) reaches directlythe listener P2 in the front passenger seat. Further, in case of FIG. 4,the speaker unit SP1 and the listener P1 in the driver's seat virtuallyface each other as described in FIG. 3, and, sounds radiated from thefirst R channel speaker 101 and the second R channel speaker 102 canceleach other near the first reference plane c, and so the listener P1sitting in the driver's seat feels like sound does not come from thefront.

Now, in the space inside the vehicle X and Y, such a relationship thatthe distance y1 to the listener P1 in the driver's seat and the distancey2 to the listener P2 in the front passenger seat are equal and thedistance of the path a through which sound is reflected by thereflecting plane A and reaches the listener P1 in the driver's seat fromthe first R channel speaker 101 of the speaker unit SP1 and the distanceof the path through which sound reaches directly the listener P2 in thefront passenger seat from the second R channel speaker 102 are equal,can be represented as follows.

y1=y2=y  Condition 1:

path α=path β  Condition 2:

Path α=((x1+x3)²+(y1)²)^(0.5)  (Equation 2)

Path β=((x2−x3)²+(y2)²)^(0.5)  (Equation 3)

The following equation 4 can be derived from the condition 2 and theabove equations 2 and 3. Equation 5 can be obtained by applying thecondition 1 to the equation 4 and figuring out x3.

((x1+x3)²+(y1)²)^(0.5)=((x2−x3)²+(y2)²)^(0.5)  (Equation 4)

x3=0.5*(x2−x1)  (Equation 5)

According to the above equation 5, the speaker unit SP1 needs to bearranged in the location at the distance x3 which is spaced apart fromthe reflecting plane A by a half of the distance between the twolisteners P1 and P2.

Although the positions of the speaker unit SP1 of the driver's seatside, the listener P1 in the driver's seat and the listener P2 in thefront passenger seat are described above, the same applies to thearrangement of the speaker unit SP2 of the front passenger seat side.

As long as the arrangement shown in FIG. 4 is realized, it is possibleto provide a listening environment which does not give a sense ofdiscomfort to listeners P1 and P2. However, FIG. 4 shows an example of acase where listeners P1 and P2 do not move, and, if the positions of theheads of listeners P1 and P2 (hereinafter “positions of listeners” orsimply “listeners P1 and P2”) move back and forth or right and left,there is a case where the above optimal listening positions are shiftedand listeners P1 and P2 listening to sound from the speaker system 100feel a sense of discomfort. To be more specific, if the position of thelistener is shifted from a null plane (a plane in which sound based onthe in-phase signal and sound based on the reverse phase signal canceleach other), sound comes from a speaker unit which assumingly does notexist and stereo sounds of the right and left speakers (one is a virtualimage) are undermined. Further, a sense of discomfort is caused by thedifference between the sound volume levels before and after movement andbetween the sound volumes of the right and left speakers.

For example, in the speaker system 100 of FIG. 1, if the driver or thelistener sitting in the front passenger seat moves the seat back andforth as shown in FIG. 2 or changes the reclining angle, the head of thedriver or the listener in the front passenger seat moves back and forthand consequently the listening position moves back and forth. In view ofthe above background, the speaker system 100 detects the current firstand/or second listening positions if the location of the listenerchanges and, according to the detection result, automatically adjuststhe opening angles of the speakers 101 to 104, the differences of anglesof elevations between the speakers 101 to 104 and the angles ofelevation of the speaker units SP1 and SP2 (hereinafter referred to as“such as directions of the speakers 101 to 104”). Details will bedescribed below.

[Automatic Adjustment of Listening Positions] [Adjustment Factors]

If the position of the listener moves, the following factors need to befocused upon to adjust such as directions of the speakers 101 to 104.

1. Upon Change Back and Forth

Shift in the null plane (little)

Change in the directivity axis of the speaker (moderate)

Change in the path length through which sound is reflected by thereflecting plane and reaches the listener (little)

2. Upon Change Right and Left

Shift in the null plane (significant)

Change in the directivity axis of the speaker (little)

Change in the path length through which sound is reflected by thereflecting plane and reaches the listener (significant)

3. Upon Change Up and Down

Change in the directivity axis of a speaker

Further, the above 1. to 3. are factors taking into account one speaker(for example, the first R channel speaker 101) that reflects sound onthe reflecting plane and transmits sound to the listener. A change inthe directivity axis of the speaker, a change in the path length and achange in the difference between the right and left paths, except theshift in a null plane, cause a change in the sound volume. Further, achange in the sound volume of the above speaker spreads to the soundvolume difference from the other speaker (for example, the third Rchannel speaker 103) that transmits sound directly to the listener.

FIG. 5 is a schematic view illustrating the relationship between thepositions of the speaker unit and the listener if the positions of thelistener changes back and forth. FIG. 6 is a schematic view illustratingthe relationship between the positions of the speaker unit and thelistener if the location of the listener changes right and left. Thesymbol “” in the figure represents listeners P1 and P2, and P1′represents the position after the listener P1 moves. Further, the solidlines connecting the speaker units and the listeners represent the pathsfrom the speaker units to the listeners. However, these solid lines donot represent the directivity axes of the speakers. Further, the boldbroken line in the figure represents the null plane before change andthe bold chain line in the figure represents the null plane after thechange.

First, the above factors if the position of the listener P1 changes backand forth (that is, “shift in a null plane,” “change in a directivityaxis of the speaker,” “change in the path length through which sound isreflected on the reflecting plane and reaches the listener”) will bedescribed.

As shown in FIG. 5, the listener P1 in the driver's seat (i.e. driver)moves forward and is located at P1′. The listener P2 in the frontpassenger seat does not move. In case of forward movement, the nullplane (i.e. a plane in which sound based on the in-phase signal andsound based on the reverse phase signal cancel each other), in which theright and left path lengths from the speakers to the listener P1 areequal, moves forward. To see the movement of the null plane withreference to the line included in the null plane, the angle of the lineincluded in the null plane changes (see the bold broken lines in thefigure to the bold chain line in the figure). The difference between theright and left paths does not change. Further, given that thedirectivity axes of the speakers are shifted from the center of thelistener P1′, the right and left speakers are supposed to be used in anarea of low speaker characteristics toward the listener. In this way, ifthe listener P1 moves back and forth, it is necessary to adjust the“shift in a null plane” and the “change in the directivity axis of thespeaker.”

Next, the above factors if the location of the listener P1 changes rightand left will be described.

As shown in FIG. 6, the listener P1 moves forward and is located at P1′.The listener P2 does not move. In case of right and left movement, theright and left path lengths from the speakers to the listener P1significantly change, thereby producing the difference between the rightand left paths and, furthermore, the null plane moves right and leftsignificantly. To see movement of the null plane with reference to aline included in the null plane, the angle of the line included in thenull plane changes significantly (see the bold broken line in the figureto the bold chain line in the figure). Further, the directivity axes ofthe speakers are shifted from the center of the listener P1′.Consequently, if the listener P1 moves to the right and left, it isnecessary to adjust the “shift in the null plane”, the “change in thedirectivity axis of the speaker” and the “change in the path length.”The “shift in the null plane” in particular is significantly greatcompared to the case of the change back and forth and therefore needs tobe adjusted sufficiently.

FIGS. 7A and 7B illustrate directivity axes of the speaker if thelocation of the listener changes up and down, and FIG. 7A shows thedirectivity axes in the horizontal direction and FIG. 7B shows thedirectivity axes in the vertical direction. In FIG. 7A, the listener P0is the center location (in which speaker characteristics are optimal) ofa directivity axis 301 of the speaker, and the listeners P1 and P2 arepositions shifted from the center of the directivity axis 301 due to upand down movement of the listeners. Further, as shown in FIG. 7B, evenif the location of the listener moves up and down, there is no change inthe side glass 210 in the vertical direction and, consequently, only theangle of elevation needs to be adjusted.

FIG. 8 is a perspective view illustrating the relationship between thepositions of the speaker unit and the listener if the location of thelistener changes right and left. The symbols P0 to P2 in the figurerepresent the positions of the listener, and P0 represents the originallocation of the listener, and P1 and P2 represents the positions of thelistener if the listener moves right and left. In FIG. 8, if theposition of the listener changes right and left (i.e. X axis direction),the shortest path 311 that connects the speaker and P0, P1 and P2 byreflection through the side glass (Y axis direction) is formed on aplane 312 encircled by the broken line of FIG. 8, and so the angle ofelevation does not change.

[Method of Adjustment]

The shift in the null plane, the change in the directivity axis of thespeaker, the change in the path length and the change in the differencebetween the right and left paths, which are mentioned above, areadjusted by operations of the speaker and speaker unit (i.e. drivingsystem by means of driving motors). The operations of the speaker andspeaker unit include the operations for adjusting “rotation,” “openingangle,” “difference of angles of elevations” and “angle of elevation.”Further, a change in the sound volume and sound volume difference thatcannot be adjusted by the operations of the speaker and speaker unit,are adjusted by signal processing in the speaker (i.e. signal processingsystem by means of the sound processing section 141). In other words, achange in the sound volume and the sound volume difference that are leftafter adjustment by the operations of the speaker and speaker unit, areadjusted by signal processing of the speaker.

First, adjustment of “rotation,” “opening angle,” “difference of anglesof elevation” and “angle of elevation” will be described.

FIGS. 9A to 9D are schematic views illustrating operations of thespeaker and speaker unit. The speaker unit SP1 is employed as anexample, the same applies to the speaker unit SP2.

As shown in FIG. 9A, the “rotation” adjustment is directed to rotatingthe speaker unit SP1 entirely to the right or to the left with respectto a point O. The direction of the null plane in which silence isgenerated in theory, can be changed by a driving motor 712 (see FIG.20).

As shown in FIG. 9B, in the “opening angle” adjustment, by driving thedriving motor 111 to widen or narrow the angles between the directivityaxes of the first R channel speaker 101/the second R channel speaker 102and a reference plane 401 while maintaining the plane symmetry withrespect to the reference plane 401, it is possible to change the pathand the angle through which sound is reflected by the side glass andreaches the listener.

As shown in FIG. 9C, the “difference of angles of elevations” refers tothe difference between the angles (hereinafter “angles of elevations”)of an directivity axis 411 of the first R channel speaker 101 of thespeaker unit SP1 and an directivity axis 412 of the second R channelspeaker 102 of the speaker unit SP1 with respect to a horizontal plane402. The “difference of angle of elevation” is adjusted by driving thespeaker by the driving motor 112 and the null plane is inclined apredetermined angle from 90 degrees with respect to the horizontal plane402, so that it is possible to change the direction of the null plane.Only the above method of using the “rotation” adjustment and this methodof using the “difference of angle of elevation” adjustment can changethe direction of the null plane. With the present embodiment, thedirection of the null plane is adjusted using the “difference of angleof elevation” adjustment and is adjusted using the “rotation” adjustmentwith Embodiment 2 (described later). Further, the control of the nullplane by the adjustment as to difference of angle of elevation is alittle complicated and therefore description will be added using FIGS.11 to 14.

As shown in FIG. 9D, in the “angle of elevation” adjustment, by wideningor narrowing angle of elevations 403 of the first R channel speaker 101and the second R channel speaker 102 with respect to the horizontalplane 402 while maintaining the angle of elevation difference between andirectivity axis 411 of the first R channel speaker 101 of the speakerunit SP1 and an directivity axis 412 (not shown in FIG. 9D) of thesecond R channel speaker 102 of the speaker unit SP1, it is possible tochange the path and the angle through which sound is reflected by theside glass and reaches the listener. The speaker unit SP1 is entirelydriven by the driving motor 113 as a method of changing the angle ofelevation while maintaining the above difference of angle of elevation.

FIG. 10 shows a table of control content of “rotation,” “opening angle”and “angle of elevation” corresponding to a change in the location ofthe listener (i.e. the location of the head) employing the listener P1in the driver's. seat (i.e. right seat) as an example. Further, FIG. 10shows an example where the direction of the null plane is controlledusing the “rotation,” and so the “difference of angle of elevation” isnot shown.

In FIG. 10, if, for example, the location of the listener moves “to thefront” from the original location, control is carried out such that therotation is made to the “left,” the opening angle is “widened” and theangle of elevation is “widened.” Similarly, if the location of thelistener moves “to the back” from the original location, control iscarried out such that the rotation is made to the “right,” the openingangle is “narrowed” and the angle of elevation is “narrowed.” Further,in case of the listener P2 in the front passenger seat (i.e. left seat),the case of the listener P1 is reversed.

[Control of the Null Plane by the Angle of Elevation DifferenceAdjustment]

Next, referring to FIG. 11 to FIG. 14, control of the null plane by theangle of elevation difference adjustment will be described.

1. Regarding Generation of the Null Plane

FIG. 11 and FIG. 12 illustrate the null plane formed in a certain planeat equal distances from two sound sources, and FIG. 11 is athree-dimensional view of the null plane and FIG. 12 is atwo-dimensional view of the null plane.

In FIG. 11 and FIG. 12, if sounds having opposite phases from oneanother are outputted from two point sound sources 501 and 502, soundpressure is equal between places at equal distances from both the soundsources 501 and 502 and sound waves of opposite signs arrive and soundfrom two sound sources cancel each other in such a place therebygenerating silence. Further, a plane in which points at equal distancesfrom both the sound sources 501 and 502 are collected becomes a verticalbisector plane of lines connecting the two sound sources 501 and 502. Aplane in which sounds from the two sound sources 501 and 502 cancel eachother in this way thereby generating silence, is defined as a null plane500.

2. Displacement of Sound Source by Changing the Difference of Angle ofElevation

FIGS. 13A and 13B illustrate the null plane of the speakers due to thedifference of angle of elevation in a state of no difference of angle ofelevation, and FIG. 13A is a perspective view of the speakers and FIG.13B is a front view of the speakers. FIGS. 14A and 14B illustrate thenull plane of the speakers due to the difference of angle of elevationin a state where the difference of angle of elevation exists, and FIG.14A is a perspective view of the speakers and FIG. 14B is a front viewof the speakers.

In FIG. 13 and FIG. 14, if the above speakers 511 and 512 are typicaldynamic speakers, the center of a speaker corn 521 included in thespeaker 511 becomes a virtual point sound source 501. Further, thecenter of a speaker corn 522 included in the speaker 512 which makes apair with the speaker 511 becomes a virtual point sound source 502. Inthe speaker system 100 in FIG. 1 and FIG. 2, the speaker 511 and thespeaker 512 correspond to the first R channel speaker 101 and the thirdL channel speaker 103, and the second L channel speaker 102 and thefourth L channel speaker 104, respectively.

Further, as shown in FIG. 13, if signals having opposite phases fromeach other are outputted at the same time in a state of no difference ofangle of elevation, the null plane 500 is formed in the verticalbisector plane with respect to the line connecting the point soundsource 502 which is the center of the speaker corn 522 and the pointsound source 501 which is the center of the speaker corn 521. If thedifference of angle of elevation as shown in FIG. 14 is provided byapplying the angle of elevation to the speaker 512 which is one of thespeakers in the state of FIG. 13, the location of the point sound source502 which is the center of the speaker corn 522 moves up. By this means,as shown in FIG. 14B, the vertical bisector plane of the line connectingthe point sound source 502 and point sound source 501 which is thecenter of the speaker corn 521 inclines consequently, so that it ispossible to incline the null plane 500. In this way, the inclination ofthe null plane 500 can be changed by the difference of angle ofelevation between the two speakers 511 and 512, and the first listeningposition and the second listening position can be placed on the nullplane 500 by changing the inclination. Further, although the null plane500 can be changed by rotating speaker units, adjustment of the nullplane 500 by rotation is carried out not by inclining the null plane 500but by moving the null plane 500 while maintaining the vertical statewhere a speaker unit is used as the axis.

[Correction of the Path Length Based on the Phase Difference]

Next, correction of the path length based on the phase difference willbe described.

FIG. 15 illustrates correction of the path length based on to the phasedifference. The symbols P1 and P2 in the figure represent the positionsof listeners, the symbol P1′ represents the location of the listener P1after leftward movement, the symbols U1 and U2 represent the positionswhere the speaker units SP1 and SP2 are arranged. Further, in thespeaker system 100 of FIG. 1, a reflecting plane 600 and a reflectingplane 620 correspond to the side glasses 210 and 220.

1. In Case the Listener P1 Moves Right and Left

Although the distance l₁ from U1 to P1 and the distance l₂ from U2 to P1are equal at the point P1, the difference is produced between thedistance l₁ and the distance l₂ to P1′ after movement. Here, the symboll₁′ refers to the distance through which the sound outputted from thespeaker unit SP1 is reflected by the reflecting plane 600 and reachesP1′ from the location U1 after movement, and the symbol l₂′ refers tothe distance through which the sound outputted from the speaker unit SP2reaches P1′ from the location U2 directly. The relational equation ofthe difference ΔL between l₁′ and l₂′ is as follows.

$\begin{matrix}{l_{1}^{\prime} = \sqrt{\left( {\frac{x_{1} + x_{2}}{2} + {\Delta \; x}} \right)^{2} + y^{2}}} & \left( {{Equation}\mspace{14mu} 6} \right) \\{l_{3}^{\prime} = \sqrt{\left( {\frac{x_{2} + x_{1}}{2} - {\Delta \; x}} \right)^{2} + y^{2}}} & \left( {{Equation}\mspace{14mu} 7} \right) \\{{\Delta \; L} = {{l_{1}^{\prime} - l_{3}^{\prime}} = \begin{matrix}{\sqrt{\left( {\frac{x_{1} + x_{2}}{2} + {\Delta \; x}} \right)^{2} + y^{2}} -} \\\sqrt{\left( {\frac{x_{2} + x_{1}}{2} - {\Delta \; x}} \right)^{2} + y^{2}}\end{matrix}}} & \left( {{Equation}\mspace{14mu} 8} \right)\end{matrix}$

The sign of Δx in the above equations 6 to 8 is positive in the leftdirection in FIG. 15.

2. Regarding Derivation of the Above Equations 6 to 8

The positions P1 and P2 are spaced apart from the plane 610 by thedistance y.

The positions P1 and P2 are located spaced apart from the reflectingplane 600 by the distance x₁ and the distance x₂, respectively.

Further, the distance x₃ from the reflecting plane 600 of U1, which isequal to the distance l₁ through which sound is reflected by thereflecting plane 600 and reaches P1 from U1 and the distance l₃connecting U2 and P1 directly, is represented by the following equation9.

$\begin{matrix}{x_{3} = \frac{x_{2} - x_{1}}{2}} & \left( {{Equation}\mspace{14mu} 9} \right)\end{matrix}$

Similarly, the distance x₄ from reflecting plane 620 of U2, which isequal to the distance l₄ through which sound is reflected by thereflecting plane 620 and reaches P2 from U2 and the distance l₂connecting U1 and P2 directly, is represented by the following equation10. Further, in the following equation 10, the symbol x₅ represents thedistance between P2 and the reflecting plane 620, and the symbol x₆represents the distance between P1 and the reflecting plane 620.

$\begin{matrix}{x_{4} = \frac{x_{6} - x_{5}}{2}} & \left( {{Equation}\mspace{14mu} 10} \right)\end{matrix}$

To make the distances l₂ and l₃ equal, the following equation 13 needsto be satisfied. The following equations 11 and 12 for deriving theequation 13 use the above-described equations 9 and 10.

from l₂=√{square root over ((x₂−x₃)²+y²)} and Equation 9,

$\begin{matrix}{l_{2} = \sqrt{\left( \frac{x_{2} + x_{1}}{2} \right)^{2} + y^{2}}} & \left( {{Equation}\mspace{14mu} 11} \right)\end{matrix}$

from l₃=√{square root over ((x₆−x₄)²+y²)} and Equation 10,

$\begin{matrix}{l_{3} = \sqrt{\left( \frac{x_{6} + x_{5}}{2} \right)^{2} + y^{2}}} & \left( {{Equation}\mspace{14mu} 12} \right)\end{matrix}$

if l₂=l₃ is solved,

x ₂ +x ₁ =x ₆ +x ₅  (Equation 13)

Further, given that the distance between P1 and P2 does not change, thefollowing equation 14 holds.

x ₆ −x ₅ =x ₂ −x ₁  (Equation 14)

Consequently, the following relational equations 15 and 16 are obtainedfrom the above equations 13 and 14.

x₅=x₁  (Equation 15)

x₆=x₂  (Equation 16)

On the other hand, if, as to the point P1′ shifted by Δx from P1, thedistance through which sound is reflected by the reflecting plane 600and reaches P1′ from U1, is the distance l₁′ and the distance connectingU2 and P1′ directly is the distance l₃′, the following relationalequations hold.

from l₁′=√{square root over ((x₁+x₃+Δx)²+y²)} and Equation 9,

$l_{1}^{\prime} = \sqrt{\left( {\frac{x_{1} + x_{2}}{2} + {\Delta \; x}} \right)^{2} + y^{2}}$

from l₃′=√{square root over ((x₆−x₄−Δx)²+y²)} and Equations 10, 15 and16,

$l_{3}^{\prime} = \sqrt{\left( {\frac{x_{2} + x_{1}}{2} - {\Delta \; x}} \right)^{2} + y^{2}}$

Consequently, the difference ΔL between the distance l₁′ to P1′ thatmoved by the distance ΔX in the X direction from P1 and the distance l₃′is represented by the following relational equation.

From ΔL=l₁′−l₃′,

${\therefore{\Delta \; L}} = {\sqrt{\left( {\frac{x_{1} + x_{2}}{2} + {\Delta \; x}} \right)^{2} + y^{2}} - \sqrt{\left( {\frac{x_{2} + x_{1}}{2} - {\Delta \; x}} \right)^{2} + y^{2}}}$

that is, the Equation 8 is determined.

3. Correction of Shifts in Arrival Times Due to Generation of theDistance Difference

If, in P1′, there is the difference between the distance l₁′ throughwhich sound is reflected by the reflecting plane 600 and reaches P1′from U1 and the distance l₃′ connecting U2 and P1′ directly, soundoutputted from U1 (for example, Rch speech) and sound outputted from U2(for example, Lch speech) does not arrive at the same time, whichproduces a shift. The time ΔT [second] which shifts in this case isdetermined as in the following equation 17 based on the path differenceΔL [m] and sound speed S [m/s]. Further, ΔL has a sign, and ΔT has asign.

ΔT=ΔL/S[second]  (Equation 17)

Consequently, to correct this shift ΔT, only sound outputted from thefirst R channel speaker 101 needs to be set by ΔT [second] ahead ofsound outputted from other speakers (from the second R channel speaker102 to the fourth L channel speaker 104) or sound outputted from otherspeakers (from the second R channel speaker 102 to the fourth L channelspeaker 104) needs to be set by ΔT [second] back of sound outputted fromthe first R channel speaker 101.

The factors of the adjusting methods if the location of the listenerchanges has been described. A case will be described below where thesemethods of adjustment are applied to the actual speaker system 100 (FIG.1). With the present embodiment, the adjustment is carried out accordingto the conditions shown in FIG. 16 and FIG. 17.

FIGS. 16A and 16B are schematic views illustrating methods of theadjustment applied to the speaker system 100 and FIG. 17 shows a tableof control content of the phase differences in the location of thelistener (i.e. the location of the head). The same components as in FIG.9 are assigned the same reference numerals.

(1) With the speaker system 100 of the present embodiment, the shift inthe null plane in which silence is generated in theory is adjusted bynot using the “rotation” adjustment of rotating the entire speaker unitbut using the “difference of angle of elevation” adjustment for thespeaker as described in detail in FIG. 13 and FIG. 14.

(2) With the speaker system 100 of the present embodiment, instead ofadjusting the “opening angle” by widening or narrowing the angle withrespect to the reference plane 401 while maintaining the plane symmetrywith respect to the reference plane 401 shown in FIG. 9, an “openingangle A 450” for adjusting with respect to the reference plane 401 onlythe opening angle of the first R channel speaker 101 which is one of thespeakers, is controlled as shown in FIG. 16A. For Lch, only the openingangle of the fourth L channel speaker 104 is adjusted in the same way.

(3) In the speaker system 100 of the present embodiment, an “angle ofelevation B460” for adjusting the angle of elevation of the overallspeaker unit is controlled as shown in FIG. 16B.

Consequently, the angle of elevation B460 of the overall speaker unitsSP1 and SP2 are controlled by the driving motors 113 and 123. Further,the difference of angle of elevation between the first R channel speaker101 and the second R channel speaker 102 installed in the speaker unitSP1 and the difference of angle of elevation between the third L channelspeaker 103 and the fourth L channel speaker 104 installed in thespeaker unit SP2 are controlled by the driving motors 112 and 122,respectively.

In this way, with the present embodiment, only the opening angle A450and the angle of elevation B460 are adjusted. By employing the method ofadjusting only the opening angle A450 and the angle of elevation B460,it is possible to reduce complexity of the mechanism and decrease cost.Further, it is more effective to adjust the opening angle and adjustpaths through which sounds are reflected by the side glasses 210 and 220than to adjust the null plane in which silence is generated in theory byrotation.

With the present embodiment, the inclination of the null plane in whichsilence is generated by providing the difference of angle of elevation,is controlled. Consequently, if the operation is limited as in theactual system, the null plane in which silence is generated in theory byslightly shifting the angle of elevation B460 up or down with respect tothe listener and adjusting the differences of angles of elevationsaccording to the table shown in FIG. 17, is adjusted such that the nullplane matches the location of the listener. In this case, if thelistener is positioned on the directivity axis of the speaker unit, anattention must be paid because the null plane in which silence isgenerated cannot be adjusted by providing the difference of angle ofelevation. Further, as to the definitions of positive and negative ofthe difference of angle of elevation in the table of FIG. 17, “positive”means that the angle of elevation of the outer speaker 101 or 104 isgreater than the angle of elevation of the inner speaker 102 or 103, and“negative” means that the angle of elevation of the outer speaker 101 or104 is smaller than the angle of elevation of the inner speaker 102 or103.

FIG. 18 is a flowchart showing automatic adjustment processing in thespeaker system 100. This flow is executed repeatedly by the CPU in thecontrolling section 150 at a predetermined cycle. Further, although thisflow employs an, example of movement in the location of the listener P1,the same adjustment processing is executed with respect to movement inthe location of the listener P2.

This program starts following the change in the location of the listenerP1 (step S1), whether or not the location of the listener P1 moved backand forth is decided in step S11. The movement in the location of thelistener P1 is decided by acquiring head location information of thelistener from the position detecting section 160 (see FIG. 2). A typicalexample where the listener P1 moves back and forth is a case where thelistener P1 moves the seat to the front or to the back or changes thereclining angle of the seat. Further, although it is difficult to detectright and left movement in the location of the listener P1 (describedlater) only by signals from the contact switches 161 and 162 installedin the seat, this movement can be detected by, for example, increasingcontact switches in the back of the seat. Further, it is possible toacquire head location information of the listener more accurately usinga location detecting means of a camera that takes an image of thevicinity of the listener's head and an image processing section, insteadof detecting positions of contact switches. Further, if the listener P1is the driver in the driver's seat, the right and left movement seemslittle likely. Further, oblique movement involves movement in thefront-back position, and is categorized as movement of the front-backposition.

If the location of the listener P1 moved back and forth in the abovestep S11, the null plane is adjusted in step S12. The controllingsection 150 carries out an arithmetic operation for adjusting the nullplane for placing the null plane above the location of the listener P1based on the amount of movement in the front-back position of thelistener P1, converts the arithmetic operation result into controlparameters and outputs the control parameters to the motor driversection 130. The motor driver section 130 drives an applicable drivingmotor (herein, driving motor 112) to reach the target value based oncontrol commands from the controlling section 150. Although, asdescribed above, there are two methods of carrying out the “rotation”and changing the “difference of angle of elevation” to adjust the nullplane, the null plane is adjusted by changing the difference of angle ofelevation with the present embodiment. The controlling section 150transmits to the motor driver section 130 the control commands forcontrolling opening angles, differences of angles of elevations andangles of elevations of the speakers 101 to 104 and speaker units SP1and SP2. By supplying the target value showing the “difference of angleof elevation” from these control commands, the motor driver section 130drives the driving motor 112 to a predetermined amount, provides adifference of angle of elevation between the directivity axis of thefirst R channel speaker 101 and the directivity axis of the second Rchannel speaker 102 and inclines the null plane (see FIG. 14), so thatit is possible to place the null plane in the location to which thelistener P1 moves.

Next, by changing the opening angle in the speaker unit SP1 in step S13,reflected sound is adjusted such that quality of sound that is reflectedand reaches the listener P1 improves. The decision criterion for thisadjustment includes sound pressure, distortion and frequencycharacteristics. The controlling section 150 stores as a table therelationship between the location of the listener P1 and the openingangle at which the reflected sound is heard the best for the listener P1and changes the opening angle referring to this table. Adjusting of theopening angle according to the present embodiment is directed toadjusting only the opening angle of the first R channel speaker 101shown in FIG. 16. The motor driver section 130 adjusts the reflectedsound by driving the driving motor 111 to a predetermined amount andchanging the opening angle of the first R channel speaker 101. By meansof the above processings, as in the case of the change to the back andforth shown in FIG. 5, the null plane is adjusted and the reflectedsound is adjusted.

Next, the difference between right and left sound volumes is adjusted inthe location of the listener P1 in step S14, and the flow proceeds tostep S21. Although the adjustment of the reflected sound (Rch in thisdescription) is finished by controlling the above opening angle, giventhat the reflected sound (Rch) is adjusted, it is necessary to adjustdirect sound (Lch) corresponding to the reflected sound (Rch). Then, bychanging the sound volume of the third L channel speaker 103, the rightand left sound volumes are adjusted to be the same. The controllingsection 150 outputs control commands for controlling the output volumesand the phases of the output sounds of the speakers 101 to 104, to thesound processing section 141. The controlling section 150 outputs thecontrol commands for changing the sound volume of the third L channelspeaker 103 to the sound processing section 141 to change the soundvolume of the third L channel speaker 103 and adjust the sound volumesof the right and left speakers to be the same.

Processings in the above step S11 to step S14 are referred to as“processing A”.

If the location of the listener P1 did not move back and forth in theabove step S11 or after the processing of the above step S14 is carriedout, whether or not the location of the listener P1 moved right and leftis decided in step S21. If the location of the listener P1 moved rightand left, the difference between the right and left paths is correctedin step S22. To be more specific, the difference between the right andleft paths is adjusted by setting the phase of the sound outputted fromthe first R channel speaker 101 composing the speaker unit SP1 ahead orback of phases of the sounds outputted from the other speakers 102 to104. As shown in FIG. 6, if the location of the listener P1 changesright and left, the right and left path lengths from the speakers to thelistener P1 significantly change, thereby producing a difference betweenthe right and left paths. The difference between the right and leftpaths produces a difference between the times the right and left soundsarrive and a shift in the right and left sounds. In this step S22, thedifference between the right and left paths is adjusted by changing thephases of the output sounds.

Next, the null plane is adjusted in step S23. The method of adjustmentis the same as in the case of the above step S12. However, in case ofchange to the right and left, as shown in FIG. 6, the null plane movessignificantly right and left compared to the case of change to the backand forth, and so the null plane needs to be adjusted significantly.

Next, by changing the opening angle in the speaker unit SP1 in step S24,reflected sound is adjusted such that quality of sound that is reflectedand reaches the listener P1 improves. The method of adjustment is thesame as in the case of the above step S13.

Next, the difference between the right and left sound volumes in thelocation of the listener P1 is adjusted in step S25, and the flowproceeds to step S31. The method of adjustment is the same as in thecase of the above step S14.

Processings of the above step S21 to step S25 are referred to as“processing B”.

If the location of the listener P1 did not move right and left in theabove step S21 or after processing of the above step S25 is carried out,the null plane is adjusted in step S31. The method of adjustment is thesame as in the case of the above step S12. The amount of adjustment ofthe null plane is little in this case.

Next, by changing the opening angle in the speaker unit SP1 in step S32,reflected sound is adjusted such that quality of sound that is reflectedand reaches the listener P1 improves. The method of adjustment is thesame as in the case of the above step S13.

Next, this flow is finished by adjusting the difference between theright and left sound volumes in the location of the listener P1 in stepS33 and adjusting the difference between the right and left soundvolumes in the location of the listener P2 in step S34. If the locationof the listener P1 moves up and down, a shift is produced with respectto the listener P1 between the directivity axes of one speaker that hasbeen adjusted (the first R channel speaker 101) and the other speaker(the third L channel speaker 103). In step S33, this difference betweenthe right and left sound volumes is adjusted such that the sound volumesof the right and left channels are the same for the listener P1, bychanging the sound volume of the inner speaker (the third L channelspeaker 103) of the speaker unit SP2. Similarly, in step S34, thedifference between the right and left sound volumes is adjusted suchthat the sound volumes of the right and left channels are the same forthe listener P2, by changing the sound volume of the inner speaker (thesecond L channel speaker 103) of the speaker unit SP1.

Processings of the above step S31 to step S34 are referred to as“processing C”.

The order to execute the above processings A, B and C can be switched.Further, the timing to execute this flow is arbitrary. For example, theprogram may be started if the location of the listener changes more thana predetermined distance and may be executed at all times and adjustmentmay be carried out in real time processing. Further, an embodiment ispossible where the flow is automatically executed if the listener isseated, sound is inputted or an audio device is energized. It naturallyfollows that the flow may be executed by a command of the listener.

As described above in detail, according to the present embodiment, thespeaker system 100 has: the first speaker unit SP1 that includes thefirst R channel speaker 101 outputting sound to be heard in the firstlistening position and the second R channel speaker 102 outputting soundto be heard in the second listening position; the second speaker unitSP2 that includes the third L channel speaker 103 outputting sound to beheard in the first listening position and the fourth L channel speaker104 outputting sound to be heard in the second listening position; thedriving motors 111 to 113 and 121 to 123 that drive at least the first Rchannel speaker 101 such that the current first listening position ispractically included in the vertical bisector plane of the lineconnecting the intersection of the first R channel speaker 101 and thedirectivity axis of the first R channel speaker 101 and the intersectionof the second R channel speaker 102 and the directivity axis of thesecond R channel speaker 102, and that drive at least the fourth Lchannel speaker 104 such that the current second listening position ispractically included in the vertical bisector plane of the lineconnecting the intersection of the third L channel speaker 103 and thedirectivity axis of the third L channel speaker 103 and the intersectionof the fourth L channel speaker 104 and the directivity axis of thefourth L channel speaker 104; and the motor driver section 130 thatdrives the driving motors 111 to 113 and 121 to 123. With thisconfiguration, even if the location of the listener moves back andforth, right and left or up and down, the speaker system 100 is able toautomatically adjust at least such as directions of the speakers 101 to104 to be suitable for the current listening position. By this means, itis possible to realize a speaker system that is able to provide alistening environment which does not give a sense of discomfort to aplurality of listeners. That is, in an environment in which there aretwo listeners in the passenger compartment of the vehicle, it ispossible to produce excellent effects at the same time that (1) thesound image is fixed in the front, (2) wide stereo sound can be providedand (3) sound of the R channel and sound of the L channel arrive at thesame time, for the two listeners, so that an optimal acousticenvironment can be realized.

Further, with the present embodiment, the direction of the null plane inwhich silence is generated in theory is adjusted using the angle ofelevation difference between the first R channel speaker 101 and thesecond R channel speaker 102 and the angle of elevation differencebetween the third L channel speaker 103 and the fourth L channel speaker104, so that it is possible to fixedly install the second R channelspeaker 102 and the third L channel speaker 103 and produce an effect ofchanging the direction of the null plane at lower cost.

Embodiment 2

An example has been described with Embodiment 1 where the shift in thenull plane in which silence is generated in theory is adjusted using the“differences of angles of elevations” between speakers. With the presentembodiment, the shift in the null plane is adjusted by “rotating” theentire speaker unit. Further, more precise adjustment is possible byadjusting the shift in the null plane by “rotating” the entire speakerunit.

FIG. 19 is a schematic view showing from above a speaker system 700according to Embodiment 2 of the present invention and the interior ofthe vehicle mounting the speaker system 700, and FIG. 20 is a blockdiagram showing the speaker system 700 shown in FIG. 19 andconfigurations around the speaker system 700. Upon description of thepresent embodiment, the same parts as in FIG. 1 and FIG. 2 will beassigned the same reference numerals and repetition of description willbe omitted.

In FIG. 19 and FIG. 20, the speaker system 700 has: a motor driversection 730 that drives driving motors 111, 121, 714 and 724 forchanging opening angles, driving motors 712 and 722 for changingrotation of the speaker units SP and driving motors 113 and 123 forchanging angles of elevations of speaker units SP; and a soundprocessing section 141 that carries out signal processing of a 2-channel(i.e. L channel and R channel) signal from a sound input section 140 towhich the sound source composed of the 2-channel signal is inputted andgenerates the in-phase signal (R), the reverse phase signal (R), thein-phase signal (L) and the reverse phase signal (L) as described above.

In FIG. 20, for the speaker system 700, in the vehicle, a controllingsection 750 that controls, for example, opening angles according tolistening positions of plurality of listeners and a position detectingsection 160 that detects the location of the head of the listenersitting in a seat by receiving signals from contact switches 161 and 162which detect the front-back position of the seat and the recliningangle, are provided.

The controlling section 750 is configured with microprocessor, acquireshead location information of the listener from the position detectingsection 160 by executing a control program which will be described laterin FIG. 21, outputs to the motor driver section 730 control commands forcontrolling opening angles, rotations and angles of elevations of thespeakers 101 to 104 and the speaker units SP1 and SP2 according to thecurrent first and second positions of listeners and outputs to the soundprocessing section 141 control signals for controlling the outputvolumes and phases of output sounds from the speakers 101 to 104. Themotor driver section 730 precisely controls the amount of driving of anapplicable driving motor according to the control commands and changesthe current values of the opening angles, the rotations and the anglesof elevations of the speakers 101 to 104 and the speaker units SP1 andSP2 to target values. Further, the sound processing section 141 changesthe sound volumes and the phases of the output sounds from the speakers101 to 104 according to the control signals from the controlling section750. The sound volumes and the phases are controlled by the soundprocessing section 141 to adjust the sound pressure level and a shift inphases due to changes of the opening angles of the speakers 101 to 104and the rotations and the angles of elevations of the speaker units SP1and SP2 by the driving motors.

FIG. 21 is a flowchart showing automatic adjustment processing of thespeaker system 700. This flow is executed repeatedly at a predeterminedtiming cycle by the CPU in the controlling section 750. The stepscarrying out the same processing as in the flow shown in FIG. 18 areassigned the same reference numerals. The letter “A” is assigned to thestep numbers of different steps.

Further, although this flow employs an example of movement in thelocation of the listener P1, the same adjustment processing is executedfor movement in the location of the listener P2.

The program starts following a change in the location of the listener P1(step S1), whether or not the location of the listener P1 moved back andforth is decided in step S11. The movement in the location of thelistener P1 is decided by acquiring head location information of thelistener from the position detecting section 160 (see FIG. 20). If thelocation of the listener P1 moves back and forth, the null plane isadjusted in step S12A. The controlling section 750 carries out anarithmetic operation for adjusting the null plane to place a null planeon the first listening position based on the amount of movement in thefront-back position of the listener P1, converts the arithmeticoperation result into control parameters and outputs the controlparameters to the motor driver section 730. The motor driver section 730drives an applicable driving motor (driving motor 712 in thisdescription) to reach this target value based on the control commandsfrom the controlling section 750. The null plane is adjusted by the“rotation” of the speaker unit SP2. Adjusting the null plane by therotation is superior to the “differences of angles of elevations”adjustment for inclining the null plane using the line included in thenull plane as a reference, in securing the required accuracy. Further,changing the rotation of the speaker unit SP2 provides an effect of moreprecisely adjusting the difference between the right and left soundvolumes.

Next, by changing the opening angle in the speaker unit SP1 in stepS13A, reflected sound is adjusted such that quality of sound that isreflected and reaches the listener P1 improves. The decision criterionfor this adjustment includes sound pressure, distortion and frequencycharacteristics. The controlling section 750 stores as a table therelationship between the location of the listener P1 and the openingangle, at which reflected sound is heard the best for the listener P1,in the internal memory in advance and changes the opening anglereferring to this table. Adjusting of the opening angles with thepresent embodiment is directed to adjusting opening angles of the firstR channel speaker 101 and the second R channel speaker 102 shown in FIG.16. The motor driver section 730 adjusts the reflected sound by thedriving the driving motor 111 to a predetermined amount and changing theopening angles of the first R channel speaker 101 and the second Rchannel speaker 102.

Next, the flow proceeds to step S21 by adjusting the difference betweenthe right and left sound volumes in the location of the listener P1 instep S14 and adjusting the difference between the right and left soundvolumes in the location of the listener P2 in step S15. Although thereflected sound (Rch in this description) is adjusted by controlling theopening angle, the reflected sound (Rch) is adjusted, and so it isnecessary to adjust direct sound (Lch) corresponding to the reflectedsound (Rch). By changing the opening angle of the speaker unit SP2 andthe sound volume of the third L channel speaker 103, the sound volumesof the right and left channels are adjusted to be the same for thelistener P1. The sound volumes of the second R channel speaker 102and/or the fourth L channel speaker 104 are adjusted such that the soundvolumes of the right and left channels become the same for the listenerP2. The controlling section 750 outputs to the sound processing section141 control commands for controlling the output sound volumes and thephases of the output sounds of the speakers 101 to 104. The controllingsection 750 adjusts the right and left sound volumes to be the same byoutputting to the sound processing section 141 control commands forchanging the sound volume of the third L channel speaker 103 andchanging the sound volume of the third L channel speaker 103. WithEmbodiment 1, the “rotation” of the speaker unit is not used. Therefore,for the listener P2, after the difference between the right and leftsound volumes in the location of the listener 1 is adjusted, adjustmentcould be carried out only in accordance with the adjustment of the soundvolumes of the speaker unit SP1 and the third L channel speaker 103.However, with the present embodiment, improvement of a sound effect isfurther realized by applying the “rotation” used to adjust the nullplane to adjust the directivity axis (the sound level and the speakercharacteristics corresponding to the directivity axis) of the speakerunit SP2.

Processings of the above step S11 to step S15 are referred to as“processing A”.

If the location of the listener P1 did not move back and forth in theabove step S11 or after processing of the above step S15 is carried out,whether or not the location of the listener P1 moved right and left isdecided. If the location of the listener P1 moved to the right and left,the difference between the right and left paths is corrected in stepS22. To be more specific, the difference between the right and leftpaths is adjusted by setting the phase of output sound from the first Rchannel speaker 101 of the speaker unit SP1 ahead or back of the phasesof output sounds of the other speakers 102 to 104.

Next, the null plane is adjusted in step S23A. The method of adjustmentuses the “rotation” as in the case of the above step S12A. In case ofchange to the right and left, given that the null plane significantlymoves right and left compared to the case of change to the back andforth, the null plane is adjusted more easily by using the “rotation.”

Next, by changing the opening angle in the speaker unit SP1 in step S24,reflected sound is adjusted such that quality of sound that is reflectedand reaches the listener P1 improves. The method of adjustment is thesame as in the case of the above step S13A.

Next, the difference between the right and left sound volumes in thelocation of the listener P1 is adjusted in step S25, the differencebetween the right and left sound volumes in the location of the listenerP2 is adjusted in step S26 and the flow proceeds to step S31A. Themethod of adjustment is the same as in the cases of the above step S14and step S15. In case of change to the right and left, similar to thecase of change to, the back and forth, the sound effect is furtherimproved by using the rotation adjustment to adjust the directivity axis(the sound level and the speaker characteristics corresponding to thedirectivity axis) of the speaker unit SP2 in step S26.

Processings of the above step S21 to step S26 are referred to as“processing B”.

If the location of the listener P1 did not move right and left in theabove step S21 or after processing of the above step S26 is carried out,the null plane is adjusted in step S31A. The method of adjustment usesthe “rotation” as in the case of the above step S12A.

Next, by changing the opening angle in the speaker unit SP1 in step S32,reflected sound is adjusted such that quality of sound that is reflectedand reaches the listener P1 improves. The method of adjustment is thesame as in the case of the above step S13.

Next, the same processings as in steps S25 and S26 are carried out insteps S33 and S34, and this flow is finished.

Processings of the above step S31 to step S34 are referred to as“processing C”.

The order to execute the above processings A, B and C can be switched.Further, similar to Embodiment 1, the timing to execute this flow isarbitrary, and, for example, the program may be started if the locationof the listener changes more than a predetermined distance and may beexecuted at all time and adjustment may be carried out in real timeprocessing.

In this way, according to the present embodiment, the speaker system 700has a driving motor 712 for rotating the first speaker unit SP1 and adriving motor 722 for rotating the second speaker unit SP2, so that,similar to Embodiment 1, even if the first and the second listeningpositions move back and forth, right and left or up and down, it ispossible to automatically adjust the directions and outputs sounds ofthe speakers 101 to 104 and realize a speaker system that is able toprovide to a plurality of listeners at the same time a listeningenvironment which does not give a sense of discomfort.

Further, with the present embodiment, if the direction of the null planein which silence is generated in theory is changed, the speakers 101 to104 are driven, so that it is possible to more precisely adjust the nullplane and the direction axes of the speakers 101 to 104 and produce anmore excellent sound effect.

Further, in the above description, the first and the second listeningpositions are determined in advance and are located near the heads ofthe listeners sitting in the driver's seat and the front passenger seat.More preferably, in case where the vehicle is a car with right-handsteering wheel, the first listening position is set near the left ear ofthe listener sitting in the driver's seat and the second listeningposition is set near the right ear of the listener sitting in the frontpassenger seat. In case where the vehicle is a car with a left-handsteering wheel, the first listening position is set near the right earof the listener sitting in the driver's seat and the second listeningposition is set near the left ear of the listener sitting in the frontpassenger seat.

The above description is an illustration of a preferred embodiment ofthe present invention and the scope of the present invention is notlimited to this.

Further, although examples have been described with the aboveembodiments where the present invention is applied to a speaker systemarranged on the dashboard in a vehicle, the speaker system may bemounted in other positions in the vehicle. Furthermore, the presentinvention is applicable to the speaker system installed in, for example,a narrow room other than in the passenger compartment.

Further, although the term “speaker system” is used with the aboveembodiments for ease of description, other terms are certainly possible,including, for example, “audio system,” “audio playback system,”“speaker apparatus mounted in the vehicle” and “audio devices mounted inthe vehicle.”

Furthermore, each circuit section forming the above speaker system, forexample, the type, number and connecting method of signal processingsections and position detecting sections are not limited to the abovedescribed embodiment.

The disclosure of Japanese Patent Application No. 2006-194812, filed onJul. 14, 2006, including the specification, drawings and abstract, isincorporated herein by reference in its entirety.

INDUSTRIAL APPLICABILITY

The speaker system according to the present invention is useful as aspeaker system installed in the passenger compartment of the vehicle.The present invention is also applicable for use in, for example,products having a plurality of speaker units. Further, the presentinvention is preferable for the speaker system installed in a narrowspace other than in the passenger compartment.

1. A speaker system comprising: a first speaker unit including a firstspeaker outputting a sound to be heard in a first listening position anda second speaker outputting a sound to be heard in a second listeningposition; a second speaker unit including a third speaker outputting asound to be heard in the first listening position and a fourth speakeroutputting a sound to be heard in the second listening position; and adriving section configured to drive at least the first speaker such thatthe current first listening position is substantially included in avertical bisector plane of a line connecting an intersection of thefirst speaker and an directivity axis of the first speaker and anintersection of the second speaker and an directivity axis of the secondspeaker, and to drive at least the fourth speaker such that the currentsecond listening position is substantially included in a perpendicularbisector plane of a line connecting an intersection of the third speakerand an directivity axis of the third speaker and an intersection of thefourth speaker and an directivity axis of the fourth speaker.
 2. Thespeaker system according to claim 1, wherein: one of the first and thesecond speakers receives as input an in-phase signal of a sound sourceand the other speaker receives as input a reverse phase signal of thein-phase signal; and one of the third and the fourth speakers receivesas input an in-phase signal of a same sound source and the other speakerreceives as input a reverse phase signal of the in-phase signal.
 3. Thespeaker system according to claim 1, wherein: the directivity axis ofthe first speaker is directed toward a first reflecting plane; thedirectivity axis of the second speaker is directed toward the secondlistening position; the directivity axis of the third speaker isdirected toward the first listening position; and the directivity axisof the fourth speaker is directed toward a second reflecting plane. 4.The speaker system according to claim 3, wherein: a path length throughwhich the sound outputted from the first speaker is reflected by thefirst reflecting plane and reaches the first listening position, and apath length through which the sound to be outputted from the thirdspeaker reaches the first listening position, are substantially equal;and a path length through which the sound to be outputted from thesecond speaker reaches the second listening position, and a path lengththrough which the sound to be outputted from the fourth speaker isreflected by the second reflecting plane and reaches the secondlistening position, are substantially equal.
 5. The speaker systemaccording to claim 1, wherein: the second and the third speakers arefixedly installed; and the driving section drives the first speaker andthe fourth speaker.
 6. The speaker system according to claim 5, whereinthe driving section changes a difference of angle of elevation of thefirst speaker with respect to the second speaker by driving the firstspeaker at least in a perpendicular direction or changes a difference ofangle of elevation of the fourth speaker with respect to the thirdspeaker by driving the fourth speaker at least in a perpendiculardirection.
 7. The speaker system according to claim 1, wherein thedriving section drives the first to the fourth speakers.
 8. The speakersystem according to claim 7, wherein the driving section rotates thefirst speaker unit or the second speaker unit.